Rotary tool sanding attachment

ABSTRACT

A sanding attachment for a rotary drive tool such as a rotary drill includes a section of tubing having a sheet of resilient padding material attached along the bottom semi-cylindrical face thereof. Clamps secured by wing nuts are attached to each end on the top portion of the tube adjacent each end. The clamps hold a replaceable sheet of sanding material, such as sandpaper, securely against the resilient padding. A drive shaft is transversely connected to the longitudinal midpoint of the tube. The drive shaft has a flexible coupling located adjacent the tube and a flange located above the flexible coupling. A coil spring in compression bears against the bottom of the flange and the attachment point between the drive shaft and the tube to bias the flexible coupling into alignment. An auxiliary handle is rotatably mounted on the drive shaft above the flange member.

United States Patent [191 McDowell ROTARY TOOL SANDING ATTACHMENT [75] Inventor: John E. McDowell, Raymond, Wash.

[73] Assignee: Richard E. McDowell, Raymond,

Wash. a part interest 22 Filed: Oct. 26, 1972 [21] Appl. No.: 301,127

[52] US. Cl. 51/170 PT, 51/376 [51] Int. Cl B241) 23/00 [58] Field of Search 51/170 R, 170 T, 376, 378, 51/170 PT [56] References Cited UNITED STATES PATENTS 522,546 7/1894 Yerger 51/176 1,609,508 12/1926 Cavicchi 51/177 1,798,633 3/1931 Rotheram 51/381 2,156,686 5/1939 Green l 51/381 2,234,109 3/1941 Culpepper 51/383 2,666,307 1/1954 Higert 51/168- 3,596,414 8/1971 Pirrello 51/109 R X 3,597,883 8/1971 Choplin..... 51/170 PT 3,619,954 11/1971 Miller 51/170 T 1 June 11, 1974 Primary Examiner--Al Lawrence Smith Assistant Examiner-Marc R. Davidson Attorney, Agent, or FirmChristensen, OConnor, Garrison & Havelka' [57] ABSTRACT A sanding attachment for a rotary drive tool such as a rotary drill includes a section of tubing having a sheet of resilient padding material, attached along the bottom semi-cylindrical face thereof. Clamps secured by wing nuts are attached to each end on the top portion of the tube adjacent each end. The clamps hold a replaceable sheet of sanding material, suchvas sandpato bias the flexible coupling into alignment. An auxiliary handle is rotatably mounted on the drive shaft above the flange member.

13 Claims, 7 Drawing Figures PATENTEBJun 1 1 new SHEET 10F 2 BACKGROUND OF THE INVENTION This invention relates to a sanding attachment for rotary drive tools.

Rotary sanding apparatuses exist in the prior art which are designed primarily for attachment to rotary drive tools, such as the chuck of an electric drill. A typical prior art sanding attachment includes a drive shaft connectable to a drill chuck. A flexible disc of heavy rubber or the like is attached to the other end of the drive shaft. A flat circular piece of sanding material such as sandpaper can be connected to the exposed face of the flexible disc.

In use, this particular type of sanding attachment has a number of drawbacks. Those who have operated such sanding attachments are aware that the sandpaper toward the periphery of the disc will tend to gouge into the surface being sanded if the drive shaft is not maintained at an angle perpendicular to the surface being sanded. This will produce a series of arcuate ridges in the surface being sanded. Such ridges are unsatisfactory since they defeat the primary purpose of producing a smooth sanded surface.

Additionally, sandpaper or other sanding material utilized with this type of prior art sanding attachment be acquired by reading the ensuing specification in conjunction with the accompanying drawings wherein:

FIG. 1 is an isometric view of the sanding attachment of the present invention;

FIG. 2 is a side elevation view in partial cross section of the sanding attachment of FIG. 1;

FIG. 3 is a partial cross-sectional view of the sanding attachment taken along section line 33 of FIG. 2;

FIG. 4 is a cross-sectional view of a portion of the sanding attachment taken along section line 4-4 of FIG. 2;

FIG. 5 is an isometric, partial view of a preferred embodiment of the sanding attachment of the present invention;

FIG. 6 is a cross-sectional view of the attachment of FIG. 5; and

FIG. 7 is a longitudinal sectional view of the attachment of FIG. 5.

wears out rather rapidly since excessive contact area between the sandpaper and the surface tobe sanded exists. Also, prior art sanding attachments generate an excessive amountof heat which rapidly degrades the sandpaper and affects the appearance of the surface being sanded.

It is an object of the present invention to provide a rotary sanding attachment for an electric drill which will always maintain a parallel relationship with respect to the surface being sanded while evenly distributing the forces on the attachment over the surface being sanded. Other objects of the present invention are to provideza sanding attachment with which conventional rectangular sandpaper sheets can be utilized; a sanding attachment from which heat is dissipated; a rotary sanding attachment which limits the contact area between sandpaper and thesurface being sanded; a sanding attachment with anauxiliary guide handle; a rotary sanding attachment with a flexible drive coupling; and a flexible coupling having two degrees of freedom which are biased toward axial alignment and two degrees of freedom which are substantially unbiased.

SUMMARY OF THE INVENTION The present invention therefore provides a surface finishing attachment for a rotary drive tool comprising an elongate base member having a bottom surface extending longitudinally of the base member, the surface being uniformly and convexly arcuate in transverse cross-section, a drive shaft means connected to the central portion of the base member, the drive shaft means including a flexible coupling adjacent the base member, the free end of the drive shaft means adapted to be connected to a rotary drive tool, and retention means on the base member for holding a flexible sheet of surface finishing material on the bottom surface 0 the base member.

BRIEF DESCRIPTION OF THE DRAWINGS A better understanding of the present invention can DESCRIPTION OF THE PREFERRED EMBODIMENTS .The preferred embodiment of the surface finishing attachment for a rotary drive tool is in the form of a sander adapted to be connected to a rotary drill chuck. The sanding attachment, generally designated 10, includes a base member preferably made from a section of rigid tube 12, composed of aluminum. A layer 14 of resilient material, such as foam padding or felt, is adhesively bonded to the bottom portion of tube 12. Preferably greater than half of the exterior of the tube 12 is covered by the layer 14. A sheet 16 of sandpaper or similar material can be superposed on the layer 14 of resilient material. Sheet 16 extends above the edges of layer 14.

. Two arcuate clamps 18 are secured to the top of the tube 12 by wing nuts 20. The edges 22 of the sandpaper sheet 16 are positioned under the clamps 18. The clamps are then secured tightly onto the top surface of the tube 12 by tightening the wing nuts 20. A drive shaft 24 is coupled to a connecting pin 26 in thetube 12, preferably on the longitudinal axis of the tube 12 and at the longitudinal midpoint of the tube 12. it

Referring now to FIGS. 2 and 3, holes 25 are provided on diametrically opposite sides of the tube 12.

Connecting pin 26 is inserted intothe holes 25. The

holes 25 lie 'on the longitudinal center plane of tube 12. Stub shaft 28, forming part of the drive shaft is con nected to the pin 26 and extends upwardly through an opening 30 in the top portion of the tube 12. Since the stub shaft 28 is connected to the midpoint of pin 26, the effective connecting point of tube 12 and drive shaft 24 lies at the longitudinal midpoint and on the longitudinal axis of the tube 12.

A flexible coupling 32 is interposed in the shaft 24 adjacent thetube 12. The coupling 32 is preferably a universal joint having one yoke thereof connected to the stub shaft 28 while the other yoke is connected to the upper half 34 of the drive shaft 24. A circular flange 36 is connected to the upper half .34 of the drive shaft 24 adjacent the universal coupling; 32. A coil spring 38 in compression bears against the bottom surface of the flange 36 and also bears against the top surface of connecting pin 26. Thus the universal coupling 32 is limited in movement about the pivot axis defined by pin 40 (FIG. 3), but is allowed to move relatively freely about the pivot defined by pin 42 (FIG. 2). This feature provides excellent contact with a surface being sanded while eliminating the gouging problems of the prior art since essentially no downward force is applied to the outer bottom edge of the tube when the shaft is flexed about coupling 32.

An auxiliary handle 44 for steadying the upper'half of the drive shaft 24 is provided with a central channel 46 through which a portion of the upper half 34 of the drive shaftextends. A pair of bearings 48 are mounted at each end of the channel 46 and are secured to the upper half 34 of the drive shaft 24. Thus the handle 44 can be grasped by hand while allowing the drive shaft 24 to rotate freely within the handle. As shown in FIG. 4, a detailed cross-section of the sandpaper hold-down clamps 18 is illustrated. A bolt 50 is secured to the top surface of the tube 12 adjacent each end thereof. Clamps 18 are preferably arcuate and conform to the'outer surface of the tube 12. One edge 52 of sheet 16 of properly sized sandpaper is wrapped from under the clamp 18 around tube 12 and over layer 14 of resilient padding material. The opposing edge 54 extends under the opposite side of the clamp 18.. The wing nut 20 is then screwed tightly down onto the clamp 18 to secure the edges 52 and 54 of the sandpaper sheet 16 onto the tube 12.

Referring now jointly to FIGS. 5, 6 and 7 a preferred embodiment of the sanding attachment is illustrated. The tubular member 60 is similar in construction to that described above. An opening 62 is cut across the top portion thereof to expose the interior of the tubular member 60. A small tube 64 is pivotally mounted along a diameter of the tubular member 60 by pin 66 secured to the tubular member 60 by a. suitable threaded fastener 68.'The center of small tube 64 coincides with the longitudinal center of member 60. Flange 70 extends upwardly from the central portion of tube 64. A yoke 72 is pivotally connected to the flange 70 by a pin 74. The pivotal axis of the yoke 72 is at right-angles to the pivotal axis of small tube 64 about pin 66. The upper portion of the drive shaft 76 is connected to yoke 72. A coil spring 78 surrounds the yoke 72 forming a part of the flexible coupling. The coil spring 78 bears on the edges 80 on the opening 60. The upper portion of the coil spring 78 bears ona flange on drive shaft 76 similarly to that described above.

The coil spring 78 thus biases or centers the drive shaft 60 with respect to the axis of small tube 64. Likewise due to a small moment arm between a pivotal axis of tube 64 and the bearing point 82 of the spring on edges 80, the tubular member is also biased or centered with respect to the pivotal axis of pin 66. In this combination the best results are obtained for use of the attachment of the present invention as a rotating sanding attachment for connection to a hand tool with a rotary drive.

The present invention has been described in relation to a preferred embodiment. It will be apparent that one of ordinary skill in the art can make various changes, alterations .and substitutions of equivalents without departing from theoriginal concept of the invention. It is intended that the inventive concept as disclosed herein be limited only by the definition contained in the appended claims.

What is claimed is:

l. A surface finishing attachment for a rotary drive tool comprising:

an elongate base member having a central portion and having a bottom surface extending longitudinally of said base member and extending continuously under and in mutually opposing directions from said central portion, said surface being uniformly and convexly arcuate in transverse cross section,

drive shaft means connected to the central portion of said base member and being oriented transversely to said base member, said drive shaft means including a flexible coupling adjacent said base member, the free end of said drive shaft means adapted to be connected to a rotary drive tool,

retention means on said base member for holding a flexible sheet of surface finishing material on said bottom surface said sheet extending continously under and inmutually .opposing directions from said central portion. 7

2. The attachment of claim 1 further comprising:

auxiliary handle means rotatably mounted on and surrounding said drive shaft means between said free end 'and said flexible coupling.

3. The attachment of claim 2 wherein said base member has a central longitudinal axis, said drive shaft means further comprising:

spring means connected to the upper portion of said drive shaft means above said flexible coupling and bearing on said base member for biasing the upper and lower portions of said drive shaft means con- 3O nected by said flexible coupling into mutual alignment such that at least the longitudinal axis of said base member is centered below the upper portion of said drive shaft means.

5 4. The attachment of claim 1 further comprising: a

layer of resilient material covering said bottom surface.

5. The attachment of claim 1, said base member comprising a cylindrical member, said retention means comprising first and second retention plates mounted on the top of said cylinder, and means for securing said plates to the top of said cylinder.

6. The attachment of claim 5 wherein said cylindrical member is a tube having an opening in the top portion thereof, said tube having a bar affixed to the interior thereof along a diameter thereof, the midpoint of said bar located substantially on the longitudinal center of said tube, said drive shaft means extending through said opening and being attached to said bar substantially at the longitudinal axis of said tube.

7. The attachment of claim 6 further comprising:

a flange on said drive shaft means above said flexible coupling,

a coil spring in compression bearing against said bar and against the bottom of said flange.

8. The attachment of claim 7 wherein said flexible coupling is a universal joint.

9. The attachment of claim 1, wherein said base member comprises a tubular member, and wherein said flexible coupling comprises a rod pivotally connected to said tubular member along adiameter of said tubular member and at the longitudinal center of said tubular member, a first drive shaft portion affixed to the center 6 portion of said rod, a second drive shaft portion pivot ally connected to said first drive shaft portion along an axis transverse to the pivotal axis of said rod.

10. The attachment of claim 9 further comprising:

6 a coil spring in compression surrounding said drive a layer of resilient material contacting the bottom cyshaft means and bearing against said second drive lindrical portion of said member and extending shaft portion and said tubular member. continuously from adjacent one end to adjacent the 11. The attachment of claim 10, wherein said tubular other end of said member to form a backing sur-' member has an opening in the top portion thereof sur- 5 face for a sheet of sanding material, rounding said drive shaft means, said coil spring beara handle rotatably mounted on said drive shaft being against the sides of said opening. tween said other end and said flexible coupling, 12. A sanding attachment for a rotary drive too] comclamp means for holding a sheet of sanding material prising: on and over substantially the entire length of said a cylindrically shaped member having ends and a 10 backing surface.

central portion and including attachment means 13. The sanding attachment of claim 12 further comfor connecting a drive shaft to the central portion prising: thereof and in transverse orientation to said mema flange on said drive shaft between said handle and bet, said coupling,

a drive shaft connected at one end to said attachment 5 a coil spring surrounding said drive shaft and coumeans, the other end of said drive shaft adapted for pling', said coil spring being in compression and attachment to said tool, said drive shaft having a having one end bearingon said flange and the other flexible coupling therein adjacent said cylindrically end bearing on said cylindrical member. shaped member, p 

1. A surface finishing attachment for a rotary drive tool comprising: an elongate base member having a central portion and having a bottom surface extending longitudinally of said base member and extending continuously under and in mutually opposing directions from said central portion, said surface being uniformly and convexly arcuate in transverse cross section, drive shaft means connected to the central portion of said base member and being oriented transversely to said base member, said drive shaft means including a flexible coupling adjacent said base member, the free end of said drive shaft means adapted to be connected to a rotary drive tool, retention means on said base member for holding a flexible sheet of surface finisHing material on said bottom surface said sheet extending continously under and in mutually opposing directions from said central portion.
 2. The attachment of claim 1 further comprising: auxiliary handle means rotatably mounted on and surrounding said drive shaft means between said free end and said flexible coupling.
 3. The attachment of claim 2 wherein said base member has a central longitudinal axis, said drive shaft means further comprising: spring means connected to the upper portion of said drive shaft means above said flexible coupling and bearing on said base member for biasing the upper and lower portions of said drive shaft means connected by said flexible coupling into mutual alignment such that at least the longitudinal axis of said base member is centered below the upper portion of said drive shaft means.
 4. The attachment of claim 1 further comprising: a layer of resilient material covering said bottom surface.
 5. The attachment of claim 1, said base member comprising a cylindrical member, said retention means comprising first and second retention plates mounted on the top of said cylinder, and means for securing said plates to the top of said cylinder.
 6. The attachment of claim 5 wherein said cylindrical member is a tube having an opening in the top portion thereof, said tube having a bar affixed to the interior thereof along a diameter thereof, the midpoint of said bar located substantially on the longitudinal center of said tube, said drive shaft means extending through said opening and being attached to said bar substantially at the longitudinal axis of said tube.
 7. The attachment of claim 6 further comprising: a flange on said drive shaft means above said flexible coupling, a coil spring in compression bearing against said bar and against the bottom of said flange.
 8. The attachment of claim 7 wherein said flexible coupling is a universal joint.
 9. The attachment of claim 1, wherein said base member comprises a tubular member, and wherein said flexible coupling comprises a rod pivotally connected to said tubular member along a diameter of said tubular member and at the longitudinal center of said tubular member, a first drive shaft portion affixed to the center portion of said rod, a second drive shaft portion pivotally connected to said first drive shaft portion along an axis transverse to the pivotal axis of said rod.
 10. The attachment of claim 9 further comprising: a coil spring in compression surrounding said drive shaft means and bearing against said second drive shaft portion and said tubular member.
 11. The attachment of claim 10, wherein said tubular member has an opening in the top portion thereof surrounding said drive shaft means, said coil spring bearing against the sides of said opening.
 12. A sanding attachment for a rotary drive tool comprising: a cylindrically shaped member having ends and a central portion and including attachment means for connecting a drive shaft to the central portion thereof and in transverse orientation to said member, a drive shaft connected at one end to said attachment means, the other end of said drive shaft adapted for attachment to said tool, said drive shaft having a flexible coupling therein adjacent said cylindrically shaped member, a layer of resilient material contacting the bottom cylindrical portion of said member and extending continuously from adjacent one end to adjacent the other end of said member to form a backing surface for a sheet of sanding material, a handle rotatably mounted on said drive shaft between said other end and said flexible coupling, clamp means for holding a sheet of sanding material on and over substantially the entire length of said backing surface.
 13. The sanding attachment of claim 12 further comprising: a flange on said drive shaft between said handle and said coupling, a coil spring surrounding said drive shaft and coupling, said coil spring being in compression and having one end bearIng on said flange and the other end bearing on said cylindrical member. 